Process for treating leather and leathers obtained



United States Patent Office 3,231,420 Patented Jan. 25, 1966 3.23l,420PROCESS FOR TREATING LEATHER AND LEATHERS OBTAINED John A. Lowell,Philadelphia, Edwin H. Kroeker. Ivyland, and Peter R. Buechlcr,Langhorne, Pa., asslgnors to Rohm & Haas Company, Philadelphia, Pa., acorporation of Delaware No Drawing. Filed July 6. 1962, Ser. No. 208,09211 Claims. (Cl. 117-142) This invention is concerned with impregnatedleathers and the improvement of leather by a treatment which involves animpregnation thereof with certain materials for the purpose of preparingit for finishing. it is partlcuiarly concerned with a treattnent whichprovides leathers having improved break, fuller substance, and improvedresistance to abrasion and scufilng.

it is already known to impregnate leathers with organic solventsolutions of certain polymeric substances and plasticizers therefor. Theproducts obtained by such treatments tend to change with time asplasticizer migration into the leather is gradually lost. When aqueoussystems are employed with vegetable-tanned leathers, especially ease andupholstery leathers where large amounts of uncombincd tannins arepresent. the penetration is hindcred by the swelling and consqucntpore-blocking caused by the aqueous systems.

in accordance with the present invention it has been found that leatherscan be improved in break and resistance to scuiilng by impregnation ofthe leather with an organic solvent solution of certain copolymerswithout the use of plasticizers.

in accordance with the present invention. the leather is impregnatedfrom the grain side with a certain polymeric material in an organicsolvent solution in such manner that the entire corium minor ispenetrated and a substantial amount of polymer is deposited within thecorlum minor and at the junction of the eorium minor and the ceriummajor. The nature of the polymer is also important in that it containsacid units which cause the polymeric substances to increase the tenacityof adherence of the corlum minor layer to the cerium major thcrebeneath.in other words. the treatment of the present invention involvessubstantially complete penetration of the corium minor and involvesconsiderable permeation or penetration of the polymer through all of theareas of the cerium minor and not merely the filling of the hairfollicles and openings to sebaceous glands.

The copolymers are water-insoluble copolymers. of a mixture ofmonoethyleniealiy unsaturated molecules comprising (a) about 3.5 toiil.5 moi percent. and preferably 6 to l2.5 moi percent. of an acid ofthe group consisting of acrylic acid. methacrylic acid. and ltaconicacid. (bl L to it moi percent. preferably L5 to 5 mol percent. of atleast one ester of an acid of the formula in which a is an integerhaving a value of i to 2. with a saturated monohydric aliphatic alcoholhaving 8 to 18 carbon atoms. (e) front l0.5 to 43 mol percent.preferably i6 to 27 mol percent of methyl. ethyl. or isobutyimethacrylate. and id) about 47 to 84.5 mol percent. prefsrably 58.5 to80 mol percent. of an ester of acrylic acid with a saturated monohydricalcohol having 1 to 4 carbon atoms. with the additional provisos thatthe total of (a) and (e) should be from to 45 mol percent and that themoi ratio of (b) to (c) should be from l:3..l to 1:6.7.

A portion of the methyl, ethyl or isobutyi mcthacryiate may be replacedwith aerylonltriie. methacrylonltrile. vinyl acetate. vinyl chloride.vlnylidene chloride. styrene. or vinyitolucne or mixtures thereofprovided the copolyiii ill

ill

(lil

mer contains at least 10.5 mol percent of methyl, ethyl, or isobutylmethacrylate after such replacement; hence the copolymer may contain upto 32.5 mol percent of one or more of the replacement monomersmentioned. In addition. small amounts of neutral hydrophilie comonomersmay be included such as hydroxyethyl acryiate, acryiamide,methacrylamide. or N-methyloiacrylamidc. The amount of such hydrophiliecomonomcrs may be as high as 5 mol percent or more of the total weightof copolymer, the upper limit being dictated by the requirement that thecopolymer be insoluble in water. It is essential. however, that thetotal amount of the monomer (c) and the hydrophilic comoaomcr should notexceed 45 mol percent.

The copolymers used in accordance with the present invention forimpregnating leather are formed of at least four different monomers asis clear from the definition above. Each is essential as equivalenteffects cannot be obtained if one of the four types is omitted. The acidcomponent (a) provides sites in the copolymer having a peculiar afilnityfor the protein component of the leather fibers. favoring retention ofthe copolymer in the leather even when it is soaking wet. as frotn rain.it also reduces the susceptibility of the copolymer to migration when asubsequently-applied coating composition in an organic solvent isapplied during finishing. The inclusion of component (b). the higheracrylutc or methacrylatc esters. imparts fiexibiiity and also solubilityin non-polar hydrocarbon solvents. and has a distinct advantage aspointed out hereinafter in that it reduces swelling of the leather. andfavors penetration. The hardening component (c). represented primarilyby methyl mcthacryiatc. is essential to avoid excessive softness.stickiness. and gumminess of the surface of the impregnated leather. itis also essential to provide the desired "break" lmprovctncnt. Withoutthis component. little or no improvement in break is obtained. it isalso essential that the sum of the acid and hardening components (a) and(c) in the copolymer amount to at least l5 moi percent in order toobtain the desired break improvement. On the other hand. the stun ofthese two components must not exceed 45 mol percent in the copolymer;otherwise. the impregnated leather shows severe grain cracking. andboardiness and feels like a plastic sheet instead of leather. The ratioof components (b) and (c) specified above must also be observed lf animprovement in break and resistance to scuillng are to be obtained whileretaining the desirable leather properties including the temper.well-rounded i'ccl. ficxlbillty. fullness. and susceptibility to bemanipulated efilclently in manufttcltlrlng operations. includingadaptability to be die-cut smoothly and evenly without difllcuity. it isto be noted that polymers of components (b) alone. (d) alone. or of amixture of (b) and (d) or of any of these types even with (a) providelittle or no improvement in break and generally provide otherundesirable qualities as well. such as excessive softness or loosencss.waxy. rubbery. or gummy instead of leathery feel.

To provide good qualities in the impregnated leather. the averagemolecular weight of the copolymer should be at least itl.(l00 but shouldnot be so high nor should the molecular weight distribution be such thatthe viscosity of a solution at C. in a solvent system by which it is tobe applied exceeds 20 centipoises when measured on a BrookficldSynehro-Lectrie viscometer model LVT using a No. l spindle at rpm.

The improvement of fullness and feel afforded by the present inventionis especially noticeable on the skins of smaller animals. such as sheep.goats and pigs. making them suitable for such products as certain typesof shoe leathers for which only the skins of larger animals as cowhldes.steerhides. and horsehides have heretofore generally been consideredsuitable. The process of the preseat invention also has the advantagethat it in many cases reduces the need for retannage or completelyeliminates such need.

The solvents that may be ttsed include alcohols, ketones, esters,hydrocarbons and chlorinated hydrocarbons. Examples include ethylalcohol, methyl alcohol, isopropyl alcohol, or tert-butyl alcohol.Examples of ltetones include acetone, methyl ethyl ketone, methylisopropyl ltetone, dilsobutyl ltetone. methyl isobutyl ketone and ethylisopropyl kctone. Examples of cthers include dioxanc, diethyl ether,tetrahydrofuran and diisopropyl ether. Examples of esters include ethylacetate, isopropyl acetate, butyl acetate, 2-cthoxycthyl acetate,2-butoxyethyl acetate, ethyl propionatc, and methyl butyratc. Examplesof ether alcohols include diethylene glycol, the monoethyl ether ofdiethylene glycol, and also the monomethyl. monopropyl, and monobulylethers of diethylene glycol. Examples of hydrocarbons inclttde benzene.toluene, xylenes; petroleum and solvent naphthas of aromatic characterand mixtures of these aromatics with aliphatics such as octane anddecane. Chlorinated hydrocarbons include methylene chloride, ethylenedichloride, pcrchlorocthyiene. chloroform, bromoi'orm, and carbontetrachloride.

The particular solvent may be composed of a single solvent material orit may be composed of a mixture of any of the materials mentionedherelnabove. Preferred solvents are the hydrophobic types of hydrocarbonor halogenated hydrocarbon type. These solvents have the advantage ofnot swelling the leather or its components and thereby avoiding thetendency of the solvent-soaked components to swell and block the poresand hinder the penetration of the solution of the polymer. All of theorganic solvent systems, whether of hydrophobic character or of theother types mentioned herelnabove. ttre characterized by substantiallyless tendency to swell the components of the leather than is generallyassociated with aqueous media.

The copoiymers may be prepared in any suitable fashion provided they areof proper molecular weight as defined herelnabove. Such copoiymers arereadily produced by copolymerizatlon in suitable solvents including anyof those mentioned herelnabove. The solvent that is to be employed forthe impregnation of the leather may be used in the preparation of thecopoiymer itself so that there is no need to recover the polymer fromthe initial solution formed and t0 redissoive such polymer.

The choice of proportions of the eontonomcrs to be used depends in partupon the flexibility or firmness desired in the product. lly using alarge total proportion of components (b) and (d) highly flexibleproducts are obtained without the use of plasticizers, whereas a lowtotal of (b) and (d) within the ranges indicated imparts greaterfirmness without causing undesirable stlll'enlng or grain cracking. Theuse of the several components of the copolymer in the preferred rangespccifled herein provides the optimum combination of propertiesobtainable by the present invention.

The concentration of the copoiymer solution may vary widely. Forexample, concentrations of iii to 30% may be employed for most of thecopoiymers. The use of higher concentrations up to 35% may bepermissible with the copoiymers of extremely low molecular weight,whereas it may be necessary to use concentrations even lower than thelower limit of the range mentioned when the copolymer is of molecularweight near the upper limit of the range given above.

The copoiymer solution may also contain additional materials such asdyes. pigments, and other polymeric materials in small proportions. Theamount of sttch additional polymeric substances should be keptrelatively low as compared to the copoiymer. ttnd it is preferably notover 25% of the weight of the copoiymer. The use of a dye or a pigmentis sometimes desirable to reduce the number of subsequent flnishcoatings when a colored fit) (iii

leather is to be produced. The proportion of pigment, however, shouldnot be enough to hinder the entry and penetration of the copolymersolution into the leather and thus prevent the complete penetration ofthe copolymer through the thickness of the corium minor. In general, theamount of pigment should not exceed 15 parts per lOO parts by weight ofthe solution used for impregnation.

Non-plastieizing oils may also be included in the impregnating solution.The solvent solution application offers advantages over aqueousimpregnation in that the leather fibers are not swollen duringapplication of the impregnating polymer and thus do not form adhesionsduring the drying process. However, if the leather is to be subsequentlywet with water. e.g. by the application of aqueous finishing coats, itis sometimes useful to apply oils which lttbricatc the leather. Thesereplace the leather fat liquor which was originally present in the grainsurface of the leather and which reduces such "aqueous adhesions butwhich can be driven from the grain surface by the application of thesolvents in the impregnating mixture.

Natural oils such as ncats-foot, coconut, sperm and cod oils can beemployed as leather lubricants. Such oils tend to migrate on laterflexing of the leather but can be prevented from doing so by theaddition of a long chain solvent-soluble molecule containing a polargroup. Examples of the latter are olcic acid, aikenyi sueclalc acidanhydrides such as octadecenyl, primary tailow amine, (CCm-alitylamlnes, such as tertiarydodeeyl amine, tertlary-pcntadecylamine, and mixtures thereof, and the monoglyccridyl glycolates ofnatttral oils such as neats-foot monoglyccrldyl glycolate. in general Vas much polar constituent as of non-polar natural oil is required toprevent migration of the oil mixture during flexing of the leather. Thetotal concentration of oils in the impregnation mixture is usually 3-7%.

The copoiymer solution may be applied in any fashion provided it isapplied under stteh conditions that time is available for adequatepenetration before extensive drying of the solution occurs. in thepreferred method, the solution is swabbed, brushed, or sprayed on thegrain sttrface only of the lettther. The swabblng, brushing. or wipingaction employed may be extended in duration as the means to assureadequate penetration and deposition, and for this purpose, the normalequipment that is used simply for coating leather is ordinarilyinadequate, since such cqttlpment involves a mere brttshing to spreadthe coating evenly over the surf..ee followed substantially immediatelyby drying. For the purpose of accomplishlag the impregnation by abrushing opera ion, it is necessary that the brushing be continued for icomparatively extended period of time while the impregnating material isapplied to the surface of the leather and malntttined thereon in wetcondition. Thus. an extended period of concurrent application andbrushing should be carried out to prevent the drying of the material onthe surface before extensive penetration can be accomplished. Hence.ordinary spraying or seasoning equipment for leather coating cannot beemployed without modification. Specially designed cqttlpment capable ofapplying heavy amounts of organic solvent solutions of polymer may beutilized.

The copoiymer solution may be applied by drumming or by application tothe flesh side, but these expedients do not provide the most favorableresults. In both these cases, deposition of the copolymer in the fleshside of the leather is more or less favored. This may be suitable forsome types of leather, such as cordovan, but it cannot provide theoutstanding improvement in break desired by the present invention whichrequires a high concentration of the copoiymer in the corium minor andrelatively little or no deposition through the corium malor.

More or less of the copoiymer may be left as a coating upon the leatherat the end of the impregnation process depending upon the particularmanner of effecting the impregnation. However, whether or not asubstantial amount of polymer material is left at the surface, it isessential that the copolytuer be forced to penetrate through the coriumminor or grain layer and to deposit the copolymer within the entirethickness thereof. and at the junction with the. coriutn major. Merefilling of hair pockets with the copolymer will not suffice. Although itis not essential to follow the impregnation treatment of the presentinvention with a finishing treatment involving the application of one ormore coats of a finishing composition. it is generally preferred toprovide such a finishing treatment.

The impregnation may be effected at room temperatureor at somewhatelevated temperatures up to 80 C.. the higher temperatures beingparticularly useful when it is desirable to obtttin an even lowerviscosity with a given concentration of certain of the copolymers.

After deposition of the copolymer within the body of the leather. theleather is subjected to a drying step. This may be carried out at roomteruperatttre or it may be accelerated by heating to somewhat elevatedtemperatures such as at about 50 to 70' C. On drying, the organicsolvent present is voiatilized. leaving the dry waterinsolublc acidcopoiymcr within the body of the leather.

The invention is. of cottrsc, applicable to full-grain leathers. btttmore particularly it is suited to snuil'ed or buffed grain leathers andimproves the break characterislie of leathers of these types, as well asimproving the resistance to sculilng and abrasion. it also renders thesubsequently finished leathers more readily repttired if any scuffingpenetrates through the finish coats.

The ability of the solution to penetrate the leather depends upon theviscosity and surface tension of the ingredients and their proportions.Viscosity can be lowered by proper selection of the solvent and byincreasing the amount of solvent. However. the desirable viscosity in aparticttlar application depends also upon the porosity of the leather ina pttrticular application. This. in turn. is affected by many factors.such as the type of skin. l.e., calf. cowhide. gout. etc.. the method oftanning. the extent of the tannage. the conditions of tanning. such aspli, the oil and grease content. previotts processes such as timing andbatin". the mechanical handling of the skin and the tanning and dryingprocesses. such as setting out and staking. and the amount of butting.

The depth of penetration is controlled primarily by the amount ofsolution applied. once the penetrablllty of the solution has beenregulated so as to allow it to penetratc in the first place. The depthof penetration is increased with increasing amounts of solution. Cowhideupper leather will absorb roughly its own weight of liquid. Since apenetration of at least l$% of the thickness of the leather is generallyrequired for best results depending on the proportion of corltun minorto corlttm maior. a i596 penetration of cowhide correspondsapproximately to application of liquid solution in weight of l5% of theWeight of the leather. and correspondingly for other proportions.Furthermore. a small amount of penetration of less than three to fivepercent of the thickness of the leather can be worse than no treatmentand ctttt result in a very coarse break which is undesirable.

As between individual skins of a particular type to be treated.particularly sheepskin. the total thickness of tito skin will vary andtherefore the proportion of thickness of the grain layer to totalthickness of the skin may vary considerably. Therefore, an averagequantity of solution per trait of area nmst be determined ttnd used fora particular run. For instance. in a particttlar run the variation ofgrain layer thickness to total skin thickness may vary from 20% to 40%and the optimum penetration for the run will then be determined at 30%.

As previously stated, a small degree of penetration with respect tothickness is more likely to be harmfttl than beneilciai. it isrecognized that attempts have been nutde to improve the characteristicsof leathers by impregnation iii lift

till

of the entire thickness of the leather. However, such total thicknessimpregnation must also be avoided in the present process because inaddition to the substantially greater cost of materials involved, intotal thickness impregnation the natural characteristics of the leatherare impaired. For instance, it is desirable that shoe upper leather becapable of absorbing perspiration vapor and dispersing it to theoutside. For this purpose high quality shoe ttppcr leather hasabsorptive qualities and vapor permeability and these characteristicsare inhibited little if any by our process of partial impregnation,whereas total thickness impregnation markedly reduces the moistureabsorptive property and vapor permeability of the leather.

The non-impregnated thickness of the leather product of the presentinvention is substantially free from the copoiymcr so that its vaporpermeability and flexibility is not substantially affected by thetreatment. it is believed that this is one of the reasons why theoverall vapor permeability and flexibility of the treated productthroughout its entire thickness is rtot reduced to such an extent as tomake the prodttet unsuitable for use as shoe tippers as is the case whenthe entire leather thickness is impregnated with the resin solution ofthe present invention. However, it will be appreciated thatcomparatively small quantities of copoiymcr may be present in theremaining thickness. or on the flesh surface, of the leather withoutreducing the natttral flexibility and vapor permeability thereofsulileiently to make the overall flexibility and vapor pearmenbilityunsatisfactory. For example. the leather may have small holes or cutspassing from the grain surface into the flesh layer through which thesolution liows when it is applied to the grain surface. Consequently.when it is stated herein that the remaining thickness of the leather issubstantially free from said copoiymcr it is meant that such remainingthickness does not contain a sufficient amount of eopoiyttter totunterialiy modify the naturttl properties thereof and-it is notintended by such term to exclude small quantities of copolynter in suchremaining thickness which are insufflcient to reduce the vaporpernteability and flexibility properties thereof to a degree which willrender the overall llcsibiiity and permeability of the leather productunsuitable for the purposes set forth. Furthermore. the statetuent usedherein that the copolymer solution is applied "to the grain surface onlydoes not exclude any kind of treatment which results in such smallquantities of coplyomer being present in the remaining thickness of thefinished product.

The impregnation of the present invention is adapted to be applied toany type of leather such as that obtained frotn the skins of calves.cattle. goats. sheep, horses. and regardless of the particular mttnnerof tanning. Thus. the leather may be that obtained by chrome tanning,zirconlttm tanning. vegetable tanning. or tanning by the use ofsynthetic tanning agents. it is particularly valttabie withchromium-tanned leather. At the time of the application of theimpregnation. the leather should generally be that obtained after thedrying of the tttnned. dyed. and/or fat-ilquored leather.

The impregnation treatment of the present invention improves the break,the filling, ttnd the resistance to abrasion and scufllng of theleather. The hnprovement is such that even with tanned leathers of poorquality. impregnated leathers of high quality can be obtained that aresuitable for use as shoe uppers, shoe linings, handbags, belts,garments. gloves. luggage. footballs. baseballs, bookbindings.upholstery and other related uses. The improvement in the break referredto is so outstanding that inferior grades of lettthers which command alow price because they ordinnriy cannot be finished into high qualityleather having good break characteristics can be treated by the presentinvention and converted into high quality leathers having goodcharacteristics as far as break is concerned. in other words, thepresent invention serves to upgrade leathers, whether the inferiority ofthe leather treated is that inherent in the particular hide from whichthe leather was produced or that resulting from the tanning and/or otheroperations by which it was produced. iiecause of this capacity of thepresent invention, it may he applied to the leathers obtained frontloose flanks and bellies which are ordinarily of sttch inferior gradethat they have been discarded or ttscd only as so-caiicd oiTal"leathers. When applied to such poor grade materials, the finishedleathers that can be obtained are so improved in quality that they canbe ttscd for the making of shoes. upholstery, bags, belts, bricfeases,etc., where high-gradc leathers are needed. in addition. sttflicicntfilling action is provided by the copolymer to firm the loose areas suchas bellies and flanks of the leather so that tnore of these articles ofcommerce can be obtained from the leather than would otherwise bepossible.

After application of the impregnation, whether or not it involves theleaving of any of the copolymcr on the surface, the leather may be, andpreferably is, finished by the application of one or more coatings. Thissubsequent coating may be any polymeric or other material normallyemployed for leather finish coatings. it may, of course, he pigmented,dyed. or not, as desired. Convemionally used finishing materials such asnitrocellulose lacquers of aqttcous dispersions or organic solventsolutions of vinyl or acrylic polymers have been found suitable forfinishing sttclt impregnated lcaihcrs.

in finishing, the surprising discovery was ntadc that the adherence ofthese leather finishes to such impregnated leather was better than tothe surface of the same leather prior to impregnation. in addition. thewet-molding qttalitles of the flnislted impregnated leathers are greatlyenhanced. This is particularly the case when the leather is plated afterapplication of one or more finish coats.

The process of the present invention is characterized particularly withthe application of hydrophlllc acid copolymers to leather in an organicsolvent system that is ill Ill)

lb. moles) 20.47 lbs. Methyl methacrylatc, inhibited with 60 p.p.m. ofmonomethyi ether of hydroquinone (0.063 lb. moles) (C -C )-itii yimcthacrylate derived from a mixed technical alcohol mixture which was 2%tctradecanol, 30% hexadecunol, and 68% octadecanol, uninhibited, 98%pure by saponification number (0.010 lb. moles) Mcthacrylic acid,inhibited with 250 p.p.m. of monomcthyl ether of hydrquinone (0.0l8 lb.moles) 6.3 lbs.

3.22 lbs.

1.57 lbs.

A catalyst solution was also made up in another vessel consisting of:

Concomitant addition of 20% of the monomeric mixture ttnd 20% of thecatalyst solution was then made to the polymerization kettle and a batchtemperature of lti-i03 C. was maintained for minutes before the rest ofthe monomeric solution and catalyst solution were added gradually andconcomitantly during 100 minutes. The batch temperature was maintainedat ll0"-lli" C. 4 Va hours; thcrcttftcr at l00-l0l C. for 2'/: hours. At7 hours, 5.07 lbs. of toluene was added and the batch allowed to cool toC. The prodttct was a toluene: cumcne solution, 40.2% of copolymer. Theyield of solids in the solution was 74 lbs., 2 01.. At 25 C., theviscosity of the 40.2% solution, as measttred on a "Synchro-Lectric"ilrooklicld viscometer, was 63 centipolscs.

The flash point ('i'ng) was 54 F. The viscosity tit 25' C. in the samesolvent bill at 20% concentration was 7.4 cps.

(h) Higher flash points are obtained when the copolytucr is made inother solvents. For example, the following runs gave the followingresults:

Percent Vise. ltnn liolvnnt Builds 20% Flash Point. Found cps.

It iioivosso Iltitl (a high flash iii h ara- 1.0 tar F. Tag.

matte salvaut naphtha bniitug la the ran a of iltltl to tan" i it i rrlvaao llltl/ttlittctt0-0il.till.l (weight 40 7.0 tatt' F. Tag.

a a. C iialvmo llm ta high flash hi it am it) 0.7 tilt 1*.0pon Cup.

utatio solvent naphtha hol tut in the range of ii'tt to M0 l.

(a) Preparnllon 0/ copolymer.-A stainless steel kettle was fitted withan agitator. a thermocouple, inlet pipe for nitrogen gas, pot forholding the monomer, funnel for catalyst solution, water-cooledcondenser, and steam-heated lncket.

The polymerization vessel was flushed with nitrogen and charged with 34lbs. of toluene and 3.83 lbs. of cumcnc which mixture was hctttcd tolOS-liO C. A monomeric mixture was made up consisting of:

Ethyl acrylate. inhibited with 200 p.p.m. of monomethyi ether ofhydroquinonc (0.205

(c) An impregnation mixture was applied to badhreaking full-grain chrometanned, lightly vegetable rctanncd calfskin by swabblng on two wet coatswith a felt swab. The first coat was applied with a dripping wet swabwhich was rewet often to keep it saturated. Then before the polymercould "set or dry due to the absorption of the solvent by the leather, asecond wet cent was applied in a shnilar fashion. Uptake of the solventsolution by the leather was 38% of its original dry weight. fl'lfi:composition of the ltnpregnation mixture was as o ows:

The leather was dried and then finished with a conventional plated blackfinish. it was compared with other calfskins from the same lot ofleather which had been similarly finished. The unlmprcgnated calfskinsall showed good break near the backbone which rapidly worsened as testsof leather break were made at intervals moving ottt toward the peripheryof the hide. Even the ntedian area between backbone and flanks showedpoor break on these skins. The flank area itself was loose and very badbreaking. The overall appearance and feel of the unimpregnated leatherswas flat and a little unicatiterlike and papery in feel.

The impregnated finished leather on the other hand showed a fine tightrolling break in all parts, even in the flank areas. The leather feltfull and supple throughout. This fullness was outstanding in the flankareas in contrast to the unintprcgnated skins.

Scull resistance of the impregnated leather was outstandlag. Vigorousscufling across the unimpregnated leathers with a United States coin of50 cents denomination produccd extensive rupture of flbers. However, asimilar scrubbing across the impregnated leather produced no citangeexcept for a slight increase in gloss where it had been scrttbbed.Prolonged scrubbing led to melting of tlte finish frottt the frictionalheat before flber rupture occurred.

Example 2 (a) A copolynter was made by a process similar to that inExample l(u), except that the monomer composition was:

Moi percent lithyi acrylatc 6i Methyl ntctltacrylale 28 Mcthacryiatcfront same mixed alcohol mixture tts in Example 1 Methacryiic acid 6ingredients: Parts by weight Polymer solution front section (a) of thisexample Soivesso i itaw neats-foot oil (20' cold lest) ()iclc acid Theleather was dried and then finished with a convenlionul black shoe upperleather llnish attd was compared with an unltnpregnated bttt similarlyfinished adiacent section of leather from the same hide. The impregnatedieatitcr showed improved break characteristics, and intproved scuiiresistance over the unimprcgnated section without noticeably detractingfrortt the leather temper.

Example 3 Polymers were prepared in appropriate solvents by theprocedure of Example l(n) from mixtures of monomers in the proportionsgiven herelnbeiow.

3.5 ntol percent ofltaconic acid 30 ntol percent of ethyl ntcthacrylate4.5 ntol percent of octadecyl acrylate 62 mol percent of butyl acryiate12 mol percent of acrylic acid 33 ntoi percent of lsobulyl methacryiatell ntol percent of n-octyi acrylate 47 mol percent of methyl acrylateiii fill

75 till! 3.5 moi percent of itaconie acid 12.5 mol percent of methylmethacrylate 5 mol percent of vinyitoiuene 5 mol percent of dodecyiacrylate 74 mol percent of ethyl aeryiate 3.5 mol percent of itaconicacid 12.5 mol percent of methyl metltacrylate 10 moi percent ofvinylidene chloride 5 ate] percent of dodecyi acryiate 69 mol percent ofethyl acrylate 3.5 ntol percent of itaeonie acid l2.5 mol percent ofmethyl methttcrylate 6 mol percent of acrylonitrlle 5 mol percent ofdodecyi acrylate 73 moi percent of ethyl acrylate 3. mol percent ofitacoalc acid l2.5 ntol percent of methyl mcthacrylate 2 mol percent ofvinyl acetate 2 ntol percent of vinyl chloride 2.5 ntol percent ofacryionltrile 50 mo percent of ethyl acrylate 22.5 mol percent of methylacryiate 5 atol percent of dodecyi acrylate impregnating compositionswere made from each of the polynters prepttrcd front the mixtures (a)through (I) by diluting the copolymers with a mixture of xylene andethylene chloride to fornt 22% solutions. The solutions were applied inthe same manner as described in Example ltc). The leathers thusimpregnated were tested in the same manner as in Example lie). Similarimprovements in break and seufi resistance were obtained while retainingdesirable leather temper.

We claim:

I. A process for treating icatlter which comprises intpregnating theleather on the grain side only with an organic solvent solutioncontaining about l0% to 35% by weight of a water-insoluble eopolymcr ofmonocthylenlcally unsaturated molecules comprising (a) about 3.5 toltl.5 ntol percent of at least one acid selected front the groupconsisting of acrylic acid, methaerylic acid. ttnd itacouic acid. (b)about L5 to ll moi percent of ttt least one ester of an tteid of theformula where I! is an integer having a value of l to 2, with asaturated monohydrlc aliphatic aleoltoi having 8 to ill cartton atoms,(c) front l0.5 to 43 mol percent of at least one methacrylute selectedfrom the group consisting of methyl. ethyl. and lsohutyl methacrylate,and (d) about 47 to 84.5 mol percent of at least one ester of acrylicacid with a saturated ntonohydrlc alcoltol having l to 4 carbon atoms,the total of (a) and (c) being to 45 mol percent and the met rtttlo of(b) to (e) being from 1:3.3 to 1:6.7, the copolymer having an averagemOiCC ular weight of at least l0,tl00 and a viscosity not exceedingcentipolses in a 20% solution at C. in the organic solvent in which itis applied, any pigment in the solution not exceeding 15 parts by weightper lOO parts by weight of the solution, the impregnation being effectedto penetrate through the cerium minor and to deposit copolymer down tothe iunction of the corium minor with the cerium major, the remainingthickness of the leather being substantially free of the copolymer.

I lit part it!) the hansoyl peroxide was replaced with ma alttttyrontrlla as the catalyst.

2. A process as defined in claim 1 in which the copolymer also comprisesup to 32.5 mol percent of at least one monomer selected from the groupconsisting of acryionitrile, methacryionitrile, vinyl acetate, vinylchloride, vinyiidene chloride, styrene, and vinyl toluene.

3. A process as defined in claim 1 in which the copolymer also comprisesup to mol percent of neutral hydrophilic monomer selected from the groupconsisting of hydroxyethyl acrylate, acrylamide, methacrylamide, andN-methylol-acrylamide.

4. A process as defined in claim 2 in which the copolymer also comprisesup to 5 mol percent of neutral hydrophliic monomer selected from thegroup consisting of hydroxyethyl acrylate, acrylamide, methacryiamide,and N-mcthylol-ncrylamide.

5. A process as defined in claim 1 in which the copolymer also comprisesup to 32.5 mol percent of at least one monomer selected from the groupconsisting of aerylonltrile methacrylonltriie, vinyl acetate, vinylchloride, vinylidene chloride, styrene, and vinyl toluene, and also upto about 5 mol percent of neutral hydrophilic monomer selected front thegroup consisting of hydroxyethyl acrylate, acrylamide, methaeryiamldc,and N-methyiol-acrylamide.

6. A process according to claim 1 in which the copolymer is a copolymerof ethyl acrylate, methaerylic acid, methyl methacryiate, and (C -C)-alkyl methacrylate.

7. As an article of manufacture, a leather having, distributed throughthe corlum minor, a water-insoluble copolymer of (a) about 3.5 to 18.5mol percent of at least one acid selected from the group consisting ofacrylic acid, methacrylic acid, and ltaconic acid, (b) about 1.5 to 8mol percent of at least one ester of an acid of the formula where n isan integer having a value of 1 to 2, with a saturated monohydrlcaliphatic alcohol having 8 to 18 carbon atoms, (e) from 10.5 to 43 molpercent of at least one methacrylate selected front the group consistingof methyl, ethyl. and lsobutyi methacryiate, and (d) about 47 to 84.5mol percent of at least one ester of acrylic acid with a saturatedmoaohydric alcohol having 1 to 4 carbon atoms, the total of (a) and (e)being to 45 mol percent and the moi ratio of (b) to (c) being from 1:3.3to l:6.7, the copolymer having an average molecular weight of at least10,000 and a viscosity not exceeding centlpoises in n 20% solution at C.in the organic solvent in which it is applied, the remaining thicknessof the leather being substantially frre of the copolymer.

8. An art cle as defined in claim 7 in which the copolymer comprises upto 32.5 mol percent of at least fill one monomer selected from the groupconsisting of acrylonitrile, methacryionitrile, vinyl acetate, vinylchloride, vinylidcnc chloride, styrene, and vinyl toluene.

9. An article as defined in claim 7 in which the copolymer comprises upto 5 mol percent of neutral hydrophilic monomer selected from the groupconsisting of hydroxyethyl acrylate, acryiamide, methacrylamide, andN-methyloi-acrylamide.

10. An article as defined in claim 7 in which the copolymer comprises upto 32.5 mol percent of at least one monomer selected from the groupconsisting of acrylonitriie, methacrylonitriie, vinyl acetate, vinylchloride, vinylidcne chloride, styrene, and vinyl toluene, and alsocomprises up to about 5 mol percent of neutral hydrophiiic monomerselected from the group consisting of hydroxyethyl acrylate, acrylamide,methacrylamide, and N-methylol-aerylamide.

11. As an article of manufacture, a leather having, distributedthroughout the corium minor, a water-insoluble copolymer of (a) about 6to 12.5 mol percent of at least one acid selected from the groupconsisting of acrylic acid, methacrylic acid, and itaconic acid, (b)about 1.5 to 5 mol percent of at least one ester of an acid of theformula wherein n is an integer having a value of l to 2, with asaturated aliphatic monohydric alcohol having 8 to 18 carbon atoms, (1.)from 16 to 27 mol percent of at least one ntethacrylate selected fromthe group consisting of methyl, ethyl, and lsobutyl methacryiate, and(d) about 58.5 to 80 mol percent of at least one ester of acrylic acidwith a saturated monohydrlc alcohol having 1 to 4 carbon atoms, thetotal of (a) and (c) being 15 to mol percent and the ratio of (b) to (c)being from 1:3.3 to l:6.7, the copolymer having an average molecularweight of at least 10,000 and a viscosity not exceeding 20 centipolsesin a 20% solution at 25 C. in the organic solvent in which it isapplied, the remaining thickness of the leather being substantially freeof the copolymer.

References Cited by the Examiner UNITED STATES PATENTS RICHARD D.NEVINS, Irlntary Exam/var.

1. A PROCES FOR TREATING LEATHER WHICH COMPRISES IMPREGNATING THELEATHER ON THE GRAIN SIDE ONLY WITH AN ORGANIC SOLVENT SOLUTIONCONTAINING ABOUT 10% TO 35% BY WEIGHT OF A WATER-INSOLUBLE COPOLYMER OFMONOETHYLENICALLY UNSATURATED MOLECULES COMPRISING (A) ABOUT 3.5 TO 18.5MOL PERCENT OF AT LEAST ONE ACID SELECTED FROM THE GROUP CONSISTING OFACRYLIC ACID, METHACRYLIC ACID, AND ITACONIC ACID, (B) ABOUT 1.5 TO 8MOL PERCENT OF AT LEAST ONE ESTER OF AN ACID OF THE FORMULA